How to extract data meet specified condition from a matrix?

Question

Lei 2012-4-26

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Hello everyone, I have a text file which looks like below

DLS: 16-24-48-26W4   747.88  746          Sandstone
DLS: 16-24-48-26W4   746  744.88          Sandstone
DLS: 16-24-48-26W4   744.88  744.19       Sandstone
DLS: 16-24-48-26W4   744.19  741.63       Siltstone
DLS: 16-24-48-26W4   741.63  741.33       Mudstone
DLS: 16-24-48-26W4   741.33  740.96       Sandstone
DLS: 16-24-48-26W4   740.96  740.77       Mudstone
DLS: 16-24-48-26W4   740.77  739.74       Coal
DLS: 16-24-48-26W4   739.74  739.64       Mudstone and siltstone
DLS: 16-24-48-26W4   739.64  738.92       Sandstone
DLS: 16-24-48-26W4   738.92  738.74       Siltstone
DLS: 16-24-48-26W4   738.74  738.64       Coal
DLS: 16-24-48-26W4   738.64  738.55       Mudstone
DLS: 16-24-48-26W4   738.55  738.37       Coal
DLS: 16-24-48-26W4   738.37  737.87       Siltstone
DLS: 16-24-48-26W4   737.87  737.45       Siltstone
DLS: 16-24-48-26W4   737.45  737.23       Mudstone
DLS: 16-24-48-26W4   737.23  737.13       Siltstone
DLS: 16-24-48-26W4   737.13  737.08       Mudstone
DLS: 16-24-48-26W4   737.08  736.62       Coal
DLS: 16-24-48-26W4   736.62  735.89       Sandstone
DLS: 16-24-48-26W4   735.89  735.09       Sandstone
DLS: 16-24-48-26W4   735.09  734.48       Sandstone
DLS: 16-24-48-26W4   734.48  733.62       Sandstone

I wanna extract depth information for different types of rocks such as sandstone, claystone,coal etc. The depths are the third and fourth columns.I think there should be some ways to write a loop to extract these data, but I dont know how to do it. Please let me know if anyboday know how to do it or advice. Thanks.

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Krishna 2012-4-26

Hi,

Import the text file into Matlab. Try to convert it into cell array. once you have the data in cell format you can extract the row data by comapring teh strings using strcmp. If you have trouble importing the file into matlab probably it needs some preprocessing. Hope this helps.

Lei 2012-4-26

Hi Krishna,

I have no problem to import this data.I can use textscan. If I use textscan, the results would be in a cell.The thing is that I dont know how to use string variables.I will take a look at the strcmp one. Thanks for your help!

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Answer 1

Image Analyst 2012-4-26

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https://ww2.mathworks.cn/matlabcentral/answers/36660-how-to-extract-data-meet-specified-condition-from-a-matrix#answer_45858

You say "I am not importing these data into matlab." Have you considered Excel? It will be able to handle this, plus do sorting by rock type, various kinds of plotting, or whatever.

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Lei 2012-4-26

Hi

I used textscan to import my dataset into matlab

fid=fopen('ECC_LAS_10_Lithlogs.txt');

A=textscan(fid,'%s%s%s%s%s');

And now i am trying to use cellfun plus strcmp funtions to extract specific lithology depth information.

However,I found that after I use textscan,the cell A. For example,A{:,5} which is the lithology cell,does not have single quotation marks.

Because i am trying to use this code:

a = {'OL',4;'WR',7;'OL',3;'AT',2}

c=arrayfun(@(x) strcmp(x,'OL'),{a{:,1}});

I dont know why

Lei 2012-4-26

B=arrayfun(@(x) strcmp(x,'sanstone'),{A{:,5}});

the returned result is zero. I guess the reason is that after I use textscan. My A{:,5} is not string cauz i looked at these data. they dont have quotaion marks

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